Doubt in non rational equation

Have a look at this irrational equation
Its domain is [1;+infty).
The main math packages (Derive, Maple and Mathematica) we have here, at school, give x = 0 and x = 2, both as solutions!
Actually if you square twice, at last you get:
x² - 2x = 0
that leads to x = 0 and x = 2, but x = 0 IMHO is not a solution...

If you limit yourself to real numbers, then indeed x=0 is not a solution since sqrt(-1) is not a real number. If one squares both sides of the equation twice as mentioned, then solves the resulting quadratic, x=0 is considered an extraneous solution, unless complex solutions are assumed.